Engines with catalytic converters typically include Exhaust Gas Oxygen (EGO) sensors for on-board catalyst monitoring. For engines capable of utilizing multiple fuel types, the EGO sensors can provide feedback to determine conversion efficiencies of the catalytic converter for exhausts from the fuel delivered.
One prior approach for monitoring the performance of a catalytic converter involves comparing a ratio indicative of catalytic converter exhaust gas conversion efficiency determined from upstream and downstream exhaust gas sensor signals to a ratio threshold value that is indicative of a malfunctioning catalytic converter and that is adaptively adjusted in dependence on the current composition of a first and second fuel. As a result, a degraded catalyst can be identified in engines utilizing multiple fuels.
The inventors have recognized that rather than, or in addition to, adjusting a threshold ratio with fuel composition, information related to the sensor ratios may be used to identify or further estimate fuel composition, such as ethanol content and/or sulfur content. In one example, the inventors have provided systems and methods for identifying a composition of fuel based on information from front and rear exhaust oxygen sensors, where the composition may include a concentration of a constituent in fuel combusted upstream of the catalyst.